Sound processor for a cochlear implant

Abstract

The sound processor and method uses a model of basilar membrane motion to select stimuli, based upon the predicted motion which the acoustic signal presented would produce in an acoustically excited normally hearing cochlea. The filter; used, in contrast to single channel per electrode approaches, cover multiple channels and overlap with each other. Consequently the stimuli presented produce a neural excitation pattern which approximates the spatio-temporal travelling wave observed on the basilar membrane in an acoustically excited normally hearing cochlea. Preferably, the predicted electrode stimuli are based upon the instantaneous predicted amplitude of the electrode location.

The invention claimed is: 
     
       1. A sound processor for generating electrical stimuli in an auditory prosthesis having an electrode array implanted in a cochlea, the sound processor comprising:
 a microphone; 
 an analog-to-digital converter electronically coupled to the microphone to receive electronic signals from the microphone, wherein the electronic signals are generated in response to a sound signal, and the analog-to-digital converter is adapted to convert the electronic signals into digital samples; 
 a processor electronically coupled to the analog-to-digital converter to receive the digital samples, the processor being adapted to calculate a traveling wave pattern from the digital samples and generate a stimulus pattern from the calculated traveling wave pattern; and 
 an output signal generator in electronic communication with the processor, the output signal generator being adapted to generate a neural excitation signal from the stimulus pattern and output the neural excitation signal to the electrode array such that the electrode array presents the neural excitation signal and stimulates a neural excitation pattern in the cochlea which approximates a spatio-temporal pattern associated with a traveling wave generated on the basilar membrane in a normally-hearing cochlea when stimulated by the sound signal. 
 
     
     
       2. The sound processor of  claim 1 , wherein the processor calculates the traveling wave pattern by processing the digital samples according to a predetermined instruction set. 
     
     
       3. The sound processor of  claim 2 , wherein the predetermined instruction set includes a data feedback loop. 
     
     
       4. The sound processor of  claim 3 , wherein the data feedback loop generates an estimate of an amount of neural excitation resulting from the stimulus pattern and incorporates the estimate into the predetermined instruction set. 
     
     
       5. The sound processor of  claim 1 , wherein the processor calculates a neural excitation level at each electrode position in a normally-hearing cochlea when stimulated by the sound signal. 
     
     
       6. The sound processor of  claim 5 , further including:
 a half-wave rectifier, wherein the neural excitation level is calculated using the half-wave rectifier. 
 
     
     
       7. The sound processor of  claim 1 , wherein the processor is adapted to generate the stimulus pattern based upon an instantaneous amplitude of the calculated traveling wave pattern at each respective electrode position. 
     
     
       8. The sound processor of  claim 7 , wherein the instantaneous amplitude is a local maximum amplitude of the calculated traveling wave pattern at each respective electrode position. 
     
     
       9. The sound processor of  claim 1  further comprising a programmable memory electronically coupled to the processor. 
     
     
       10. The sound processor of  claim 1  further comprising a signal amplifier electronically coupled between the microphone and the analog-to-digital converter. 
     
     
       11. The sound processor of  claim 1 , wherein the processor:
 samples the digital samples to produce a data sample; 
 derives a vector of complex Fourier transform coefficients for the data sample; 
 multiplies the vector of the coefficients by a complex matrix representing a first amplitude and a first phase of Fourier frequency components according to electrode positions within the cochlea relative to a second amplitude and a second phase at a stapes in a normally-hearing cochlea to produce an output vector; and 
 converts values of the output vector into the stimulus pattern. 
 
     
     
       12. The sound processor of  claim 1 , wherein the processor determines a displacement of the basilar membrane at each electrode position in a normally-hearing cochlea when stimulated by the sound signal. 
     
     
       13. The sound processor of  claim 1 , wherein the processor determines a velocity of the basilar membrane at each electrode position in a normally-hearing cochlea when stimulated by the sound signal. 
     
     
       14. A cochlear implant, comprising:
 the sound processor of  claim 1 , 
 wherein the cochlear implant includes the electrode array, wherein the electrode array is adapted to be implanted in a cochlea adjacent a basilar membrane of the cochlea and outputs an electrical signal to the cochlea, the electrical signal corresponding to the neural excitation signal. 
 
     
     
       15. A sound processor for generating electrical stimuli in an auditory prosthesis having an electrode array implanted in a cochlea adjacent a basilar membrane, the sound processor comprising:
 a microphone adapted to generate electronic signals in response to a sound signal; 
 means for converting the electronic signals into digital samples; 
 means for processing the digital samples, including calculating a traveling wave pattern from the digital samples and generating a stimulus pattern from the calculated traveling wave pattern; and 
 means for generating a neural excitation signal from the stimulus pattern and output the neural excitation signal to the electrode array such that the electrode array presents the neural excitation signal and stimulates a neural excitation pattern in the cochlea which approximates a spatio-temporal pattern associated with a traveling wave generated on the basilar membrane in a normally-hearing cochlea when stimulated by the sound signal. 
 
     
     
       16. The sound processor of  claim 15 , wherein the means for processing the digital samples includes calculating the traveling wave pattern by processing the digital samples according to a predetermined instruction set. 
     
     
       17. The sound processor of  claim 16 , wherein the predetermined instruction set includes a data feedback loop. 
     
     
       18. The sound processor of  claim 17 , wherein the data feedback loop generates an estimate of an amount of neural excitation resulting from the stimulus pattern and incorporates the estimate into the predetermined instruction set. 
     
     
       19. The sound processor of  claim 15 , wherein the means for processing the digital samples includes calculating a neural excitation level at each electrode position in a normally-hearing cochlea when stimulated by the sound signal. 
     
     
       20. The sound processor of  claim 19 , further including:
 a half-wave rectifier, wherein the neural excitation level is calculated using the half-wave rectifier. 
 
     
     
       21. The sound processor of  claim 15  further comprising:
 means for amplifying the electronic signals. 
 
     
     
       22. The sound processor of  claim 15 , wherein the means for processing the digital samples bases the stimulus pattern upon an instantaneous amplitude of the calculated traveling wave pattern at each respective electrode position. 
     
     
       23. The sound processor of  claim 15 , wherein the means for processing the digital samples includes:
 sampling the digital samples to produce a data sample; 
 deriving a vector of complex Fourier transform coefficients for the data sample; 
 multiplying the vector of the coefficients by a complex matrix representing a first amplitude and a first phase of Fourier frequency components according to electrode positions within the cochlea relative to a second amplitude and a second phase at a stapes in a normally-hearing cochlea to produce an output vector; and 
 converting values of the output vector into the stimulus pattern. 
 
     
     
       24. The sound processor of  claim 15 , wherein the means for processing the digital samples includes determining a displacement of the basilar membrane at each electrode position in a normally-hearing cochlea when stimulated by the sound signal. 
     
     
       25. The sound processor of  claim 15 , wherein the means for processing the digital samples includes determining a velocity of the basilar membrane at each electrode position in a normally-hearing cochlea when stimulated by the sound signal. 
     
     
       26. The sound processor of  claim 15 , wherein the processor is adapted to generate the stimulus pattern based upon an instantaneous amplitude of the calculated traveling wave pattern at each respective electrode position. 
     
     
       27. A cochlear implant, comprising:
 the sound processor of  claim 15 , 
 wherein the cochlear implant includes the electrode array, wherein the electrode array is adapted to be implanted in a cochlea adjacent a basilar membrane of the cochlea and outputs an electrical signal to the cochlea, the electrical signal corresponding to the neural excitation signal. 
 
     
     
       28. A sound processor for generating electrical stimuli in an auditory prosthesis having an electrode array implanted in a cochlea adjacent a basilar membrane, the sound processor comprising:
 a microphone adapted to generate electronic signals in response to a sound signal; 
 a signal amplifier electronically coupled to the microphone; 
 an analog-to-digital converter electronically coupled to the signal amplifier to receive the electronic signals from the microphone, wherein the analog-to-digital converter is adapted to convert the electronic signals into digital samples; 
 a processor electronically coupled to the analog-to-digital converter to receive the digital samples, wherein the processor calculates a traveling wave pattern from the digital samples and generates a stimulus pattern from the calculated traveling wave pattern according to a predetermined instruction set by:
 determining a displacement of the basilar membrane and calculating a neural excitation level at each electrode position in a normally-hearing cochlea when stimulated by the sound signal, and 
 employing a data feedback loop based on the stimulus pattern, 
 
 a programmable memory electronically coupled to the processor; and 
 an output signal generator in electronic communication with the processor and the electrode array, the output signal generator being adapted to generate a neural excitation signal from the stimulus pattern and output the neural excitation signal to the electrode array such that the electrode array presents the neural excitation signal and stimulates a neural excitation pattern in the cochlea which approximates a spatio-temporal pattern associated with a traveling wave generated on the basilar membrane in a normally-hearing cochlea when stimulated by the sound signal. 
 
     
     
       29. The sound processor of  claim 28 , wherein the processor is adapted to generate the stimulus pattern based upon an instantaneous amplitude of the calculated traveling wave pattern at each respective electrode position. 
     
     
       30. The sound processor of  claim 29 , wherein the instantaneous amplitude is a local maximum amplitude of the calculated traveling wave pattern at each respective electrode position. 
     
     
       31. The sound processor of  claim 28 , wherein as part of the predetermined instruction set, the processor:
 samples the digital samples to produce a data sample; 
 derives a vector of complex Fourier transform coefficients for the data sample; 
 multiplies the vector of the coefficients by a complex matrix representing a first amplitude and a first phase of Fourier frequency components according to electrode positions within the cochlea relative to a second amplitude and a second phase at a stapes in a normally-hearing cochlea to produce an output vector; and 
 converts values of the output vector into the stimulus pattern. 
 
     
     
       32. The sound processor of  claim 28 , further including:
 a half-wave rectifier, wherein the neural excitation level is calculated using the half-wave rectifier. 
 
     
     
       33. The sound processor of  claim 28 , wherein the data feedback loop generates an estimate of an amount of neural excitation resulting from the stimulus pattern and incorporates the estimate into the predetermined instruction set. 
     
     
       34. A cochlear implant, comprising:
 the sound processor of  claim 28 , 
 wherein the cochlear implant includes the electrode array, wherein the electrode array is adapted to be implanted in a cochlea adjacent a basilar membrane of the cochlea and outputs an electrical signal to the cochlea, the electrical signal corresponding to the neural excitation signal.